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SubjectRe: [PATCH v7 2/3] Bluetooth: mediatek: Add protocol support for MediaTek serial devices
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Hi Sean,

>>>>>>>>>>> +
>>>>>>>>>>> +static int mtk_hci_wmt_sync(struct hci_dev *hdev, u8 op, u8 flag, u16 plen,
>>>>>>>>>>> + const void *param)
>>>>>>>>>>> +{
>>>>>>>>>>> + struct mtk_hci_wmt_cmd wc;
>>>>>>>>>>> + struct mtk_wmt_hdr *hdr;
>>>>>>>>>>> + struct sk_buff *skb;
>>>>>>>>>>> + u32 hlen;
>>>>>>>>>>> +
>>>>>>>>>>> + hlen = sizeof(*hdr) + plen;
>>>>>>>>>>> + if (hlen > 255)
>>>>>>>>>>> + return -EINVAL;
>>>>>>>>>>> +
>>>>>>>>>>> + hdr = (struct mtk_wmt_hdr *)&wc;
>>>>>>>>>>> + hdr->dir = 1;
>>>>>>>>>>> + hdr->op = op;
>>>>>>>>>>> + hdr->dlen = cpu_to_le16(plen + 1);
>>>>>>>>>>> + hdr->flag = flag;
>>>>>>>>>>> + memcpy(wc.data, param, plen);
>>>>>>>>>>> +
>>>>>>>>>>> + atomic_inc(&hdev->cmd_cnt);
>>>>>>>>>>
>>>>>>>>>> Why are you doing this one. It will need a comment here if really needed. However I doubt that this is needed. You are only using it from hdev->setup and hdev->shutdown callbacks.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> An increment on cmd_cnt is really needed because hci_cmd_work would check whether cmd_cnt is positive and then has a decrement on cmd_cnt before a packet is being sent out.
>>>>>>>>>
>>>>>>>>> okay will add a comment.
>>>>>>>>
>>>>>>>> but you are in ->setup callback this time. So if you need this, then all the other ->setup routines would actually fail as well. Either this is leftover from when you did things in ->probe or ->open or this is some thing we might better fix properly in the core instead of papering over it. Can you recheck if this is really needed.
>>>>>>>>
>>>>>>>
>>>>>>> I added a counter print and the counter increments as below
>>>>>>>
>>>>>>> /* atomic_inc(&hdev->cmd_cnt); */
>>>>>>> pr_info("cmd_cnt = %d\n" , atomic_read(&hdev->cmd_cnt));
>>>>>>>
>>>>>>> skb = __hci_cmd_sync_ev(hdev, 0xfc6f, hlen, &wc, HCI_VENDOR_PKT,
>>>>>>> HCI_INIT_TIMEOUT);
>>>>>>>
>>>>>>> and the log show up that
>>>>>>>
>>>>>>>
>>>>>>> [ 334.049156] Bluetooth: hci0: command 0xfc6f tx timeout
>>>>>>> [ 334.054840] cmd_cnt = 0
>>>>>>> [ 336.065076] Bluetooth: hci0: command 0xfc6f tx timeout
>>>>>>> [ 336.070795] cmd_cnt = 0
>>>>>>> [ 338.080997] Bluetooth: hci0: command 0xfc6f tx timeout
>>>>>>> [ 338.086683] cmd_cnt = 0
>>>>>>> [ 340.096907] Bluetooth: hci0: command 0xfc6f tx timeout
>>>>>>> [ 340.102609] cmd_cnt = 0
>>>>>>> [ 342.112824] Bluetooth: hci0: command 0xfc6f tx timeout
>>>>>>> [ 342.118520] cmd_cnt = 0
>>>>>>> [ 344.128747] Bluetooth: hci0: command 0xfc6f tx timeout
>>>>>>> [ 344.134454] cmd_cnt = 0
>>>>>>> [ 346.144667] Bluetooth: hci0: command 0xfc6f tx timeout
>>>>>>> [ 346.150372] cmd_cnt = 0
>>>>>>>
>>>>>>>
>>>>>>> The packet is dropped by hci_cmd_work at [1], so I also wondered why the
>>>>>>> other vendor driver works, it seems the counter needs to be incremented
>>>>>>> before every skb is being queued to cmd_q.
>>>>>>>
>>>>>>> 4257 static void hci_cmd_work(struct work_struct *work)
>>>>>>> 4258 {
>>>>>>> 4259 struct hci_dev *hdev = container_of(work, struct hci_dev, cmd_work);
>>>>>>> 4260 struct sk_buff *skb;
>>>>>>> 4261
>>>>>>> 4262 BT_DBG("%s cmd_cnt %d cmd queued %d", hdev->name,
>>>>>>> 4263 atomic_read(&hdev->cmd_cnt), skb_queue_len(&hdev->cmd_q));
>>>>>>> 4264
>>>>>>> 4265 /* Send queued commands */
>>>>>>>
>>>>>>> [1]
>>>>>>> 4266 if (atomic_read(&hdev->cmd_cnt)) { /* dropped when cmd_cnt is zero */
>>>>>>> 4267 skb = skb_dequeue(&hdev->cmd_q);
>>>>>>> 4268 if (!skb)
>>>>>>> 4269 return;
>>>>>>> 4270
>>>>>>> 4271 kfree_skb(hdev->sent_cmd);
>>>>>>> 4272
>>>>>>> 4273 hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
>>>>>>> 4274 if (hdev->sent_cmd) {
>>>>>>> 4275 atomic_dec(&hdev->cmd_cnt); /* cmd_cnt-- */
>>>>>>> 4276 hci_send_frame(hdev, skb);
>>>>>>
>>>>>> actually the command also needs to better go via the raw_q anyway since it doesn’t come back with the cmd status or cmd complete. You have it waiting for a vendor event. Maybe with is something we need to consider with __hci_cmd_sync_ev anyway.
>>>>>>
>>>>>> Johan would know best since he wrote that code. Anyway, we should fix that in the core and not have you hack around it.
>>>>>>
>>>>>
>>>>> yes, my case is that received event is neither cmd status nor cmd complete. It is completely a vendor event.
>>>>>
>>>>> if it wants to be solved by the core layer, do you permit that I remove the hack and then send it in the next version?
>>>>
>>>> we need to have a __hci_raw_sync_ev that uses the hdev->raw_q and waits for the specified event to come back. I never realized that you are missing the cmd status or cmd complete. So this is similar to the original CSR vendor commands which had the same behavior.
>>>>
>>>> I have the feeling that you hdev->cmd_cnt increment is just hiding the problem here. If you really think that it is not chains any side effects we can merge the driver with a big warning and fix this up. However the clean way would be for you to create a patch that introduces __hci_raw_sync_ev as describe above.
>>>
>>> What do you think of this? If I add extra atomic_set 1 on cmd_cnt after driver really got a vendor event back instead of blinding to increment for every packet sent.
>>>
>>> the behavior is the same to receive a cmd status or complete. it should not have side effects.
>>>
>>> 96 skb = __hci_cmd_sync_ev(hdev, 0xfc6f, hlen, &wc, HCI_VENDOR_PKT,
>>> 97 HCI_INIT_TIMEOUT);
>>> 98
>>> 99 if (IS_ERR(skb)) {
>>> 100 int err = PTR_ERR(skb);
>>> 101
>>> 102 bt_dev_err(hdev, "Failed to send wmt cmd (%d)", err);
>>> 103 return err;
>>> 104 }
>>> 105
>>> 106 if (!test_bit(HCI_RESET, &hdev->flags)) <<<<<<
>>> 107 atomic_set(&hdev->cmd_cnt, 1); <<<<<<
>>> 108
>>> 109 kfree_skb(skb);
>>
>> this is even more hackish since the __hci_cmd_sync_ev command is really meant to get a cmd status first before waiting for that event.
>>
>
> Understood.
>
> I've stopped the hack in v8. could we merge v8 first ? and then I will a fix up with __hci_raw_sync_ev that uses the hdev->raw_q instead of __hci_cmd_sync_ev in TODO.

so I looked into this a bit more. We actually added __hci_cmd_send for a Qualcomm firmware loader that was doing something similar. So instead of trying to add a yet another command to the core, I actually used that and implemented the wait for vendor event in the driver.

You will see my v9 on the mailing list. I also did a bunch of cosmetic minor cleanup and spelling correction. Please test this version. I also make __le16 dlen instead of dlen1 + dlen2 since I think that is what your hardware does.

If this version of the driver works for you then I am happy to merge it. You can then add support for hdev->set_bdaddr and hdev->set_diag in later patches. I also like to clean up the STP receive handler since it can be done a lot simpler and smaller, but that has to wait.

>> Are all Mediatek vendor commands this way? Or just the ones for loading the firmware? So only the WMT ones?
>>
>
> Only the WMT ones, WMT commands/events are usually used in system controlling, for example, global function on/off, firmware download, reset and so on. most only appear on device initialization

Since you never checked the result of the vendor event, I opted for just signaling that it arrived. If they can report success or failure, we need to add some extra code for that.

Regards

Marcel

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